The present disclosure relates to solar roof tiles. More particularly, it relates to photovoltaic module assemblies including a selectively implemented ballast device.
Solar power has long been viewed as an important alternative energy source. To this end, substantial efforts and investments have been made to develop and improve upon solar energy collection technology. Of particular interest are industrial- or commercial-type applications in which relatively significant amounts of solar energy can be collected and utilized in supplementing or satisfying power needs.
Solar photovoltaic technology is generally viewed as an optimal approach for large scale solar energy collection, and can be used as a primary and/or secondary (or supplemental) energy source. In general terms, solar photovoltaic systems (or simply “photovoltaic systems”) employ solar panels made of silicon or other materials (e.g., III-V cells such as GaAs) to convert sunlight into electricity. More particularly, photovoltaic systems typically include a plurality of photovoltaic (PV) modules (or “solar tiles”) interconnected with wiring to one or more appropriate electrical components (e.g., switches, inverters, junction boxes, etc.). The PV module conventionally consists of a PV laminate or panel generally forming an assembly of crystalline or amorphous semiconductor devices electrically interconnected and encapsulated. One or more electrical conductors are carried by the PV laminate through which the solar-generated current is conducted.
Regardless of an exact construction of the PV laminate, most PV applications entail placing an array of PV modules at the installation site in a location where sunlight is readily present. This is especially true for commercial or industrial applications in which a relatively large number of PV modules are desirable for generating substantial amounts of energy, with the rooftop of the commercial building providing a convenient surface at which the PV modules can be placed. As a point of reference, many commercial buildings have large, flat roofs that are inherently conducive to placement of a PV module array, and is the most efficient use of existing space. While rooftop installation is thus highly viable, certain environment constraints must be addressed. For example, the PV laminate is generally flat or planar; thus, if simply “laid” on an otherwise flat rooftop, the PV laminate may not be optimally positioned/oriented to collect a maximum amount of sunlight throughout the day. Instead, it is desirable to tilt the PV laminate at a slight angle relative to the rooftop (i.e., toward the southern sky for northern hemisphere installations, or toward the northern sky for southern hemisphere installations). Further, possible PV module displacement due to wind gusts must be accounted for, especially where the PV laminate is tilted relative to the rooftop as described above.
In light of the above, conventional PV module installation techniques have included physically interconnecting each individual PV module of the module array directly with, or into, the existing rooftop structure. For example, some PV module configurations have included multiple frame members that are physically attached to the rooftop via bolts driven through (or penetrating) the rooftop. While this technique may provide a more rigid attachment of the PV module, it is a time-consuming process and permanently damages the rooftop. Also, because holes are formed into the rooftop, distinct opportunities for water damage arise. More recently, PV module configurations have been devised for commercial, flat rooftop installation sites in which the arrayed PV modules are self-maintained relative to the rooftop in a non-penetrating manner. More particularly, the PV modules are interconnected to one another via a series of separate, auxiliary components. Ballast is mounted to the PV modules, with the ballast and interconnected PV modules serving to collectively offset wind-generated forces. Further, one or more wind-deflecting fairings (or “wind deflectors”) are assembled to some or all of the PV modules to reduce a magnitude of wind forces imparted upon an underside of the PV module and/or array.
The use of ballast to provide adequate PV module wind performance remains a necessary feature for non-penetrating PV module rooftop installations, especially for tilted PV arrangements. Because each installation site will have differing load constraints (e.g., load-carrying capacity of the roof, expected wind-related forces due to height, wind zone, and surrounding exposure of the building; etc.), the ability to adjust a weight of the ballast is beneficial. While efforts have been made to allow installers to adjust the mass or weight of ballast associated with an individual PV module, conventional designs require direct, on-site mounting of the ballast to the PV module frame, and thus entails a fairly labor intensive process. Further, the mounted ballast can create potentially damaging stresses in the PV module frame over time. Therefore, a need exists for a PV module assembly with improved ballast features.